Apparatus for forming spiral steel pipe

ABSTRACT

An apparatus for forming spiral steel pipe by spirally curling a strip of metal with a row of interior forming rolls set on an interior forming stand and rows of exterior forming rolls respectively set on exterior forming stands. A mount is provided which extends in the direction of axis of the interior forming stand in such a manner as to cover the interior forming stand wholly except the part thereof equipped with the interior forming rolls; and a plurality of rows of interior supporting rolls are disposed on the outer surface of the mount nearly in parallel with the edges of the spiralled strip.

Unite Sites atet 1191 1 1 3,916,663

Takeshita et al. Nov. 4, 1975 APPARATUS FOR FORIVHNG SPIRAL 3,650,0153/1972 Davis 29/4777 STEEL PIPE 3,776,010 12/1973 Krakow 72/12 [75]Inventors: Kazuma Takeshita, Kitakyushu;

Kenji Sam, H Ya j Primary Exammer-C. W. Lanham Shimazaki, Kit k h ll ofJapan Assistant ExaminerRobert M. Rogers Attorney, Agent, orFirm-Wenderoth, Lind & Ponack [73] Asslgnee: Nippon Steel Corporation,Tokyo,

Japan 22] Filed: Jan. 23, 1974 ABSTRACT [21] Appl, N 435,964 Anapparatus for forming spiral steel pipe by spirally curling a strip ofmetal with a row of interior forming rolls set on an interior formingstand and rows of exte- [30] Foreign Application Priority a rior formingrolls respectively set on exterior forming Jan. 24, 1973 Japan 48-11067stands. A mount is provided which extends in the direction of axis ofthe interior forming stand in such a manner as to cover the interiorforming stand Wholly [51] Int. Cl. BZIF 3/02 except the part thereofequipped with the interior Field of Search 72/49, forming rolls; and aplurality of rows of interior sup- 200 559 porting rolls are disposed onthe outer surface of the mount nearly in parallel with the edges of thespiralled [56] References Cited strip.

UNITED STATES PATENTS 3,146,331 8/1964 Schubert 72/135 6 clamslo DrawmgF'gures U.S. Patent Nov. 4, 1975 6 Sheet 10f2 3,916,663

FIG. /0 FIG. lb PRIOR ART" PRIOR ART T R A m m 3 PRIOR ART PRIOR ART US.Patent Nov. 4, 1975 Sheet 2 of2 3,916,663

APPARATUS FOR FORMING SPIRAL STEEL PIPE BACKGROUND OF THE INVENTION Thepresent invention relates to apparatus for forming helical pipe bycurling a strip of metal into a convolution.

Generally in the case of manufacturing spiral steel pipe, a strip ofsteel is curled spirally into a cylindrical pipe by using a formingapparatus, and the opposite edges of the helical convolutions of thestrip are welded.

One type of known apparatus for the manufacture of spiral steel pipe isshown in FIGS. 1a and 1b in which a row of interior forming rolls (3)set on an interior forming stand (4) and two rows of exterior formingrolls (5), (5) set on respective exterior forming stands (6), constitutean arrangement of rolls in the form of a triangle, in which the roll (3)is the apex and the rolls (5), are the base, sectionally sectionalyshown in of FIG. 1a, thereby curling strip fed continuously, into aconvolution, thus; forming pipe (2). However, in the formation of suchpipe only with the abovementioned interior and exterior forming rolls,it is difficult to maintain a constant outer diameter of the pipe. Thisdifficulty causes the edges of the strip to fail to come together at thewelding point (W), making welding operations inefficient and the qualityof the weld poor.

In order to solve the abovementioned problem in the formation of pipe,the device as illustrated in FIGS. 2a and 2b has been used. According toFIG. 2, the interior forming stand (4) has, at its head, a plurality ofinterior supporting rolls (7) disposed radially at the prescribed sizeof the inner diameter of the pipe, so that the inner diameter may bemaintained as prescribed. The addition of such rolls may be effective inthe manufacture of spiral steel pipe of better commercial value thanthat manufactured by the abovementioned triangular arrangement of rolls.

However, in the case of using the forming apparatus of FIG. 2, thespiralled strip (2) is supported from the inside only on one part of thesame, the rest being drawn toward the axis of the pipe over the interiorsupporting rolls (7), causing divergence of the edges of the strip atthe welding point (W), making it very difficult to manufacture pipe ofhigh commercial value.

Another drawback of the forming apparatus using interior supportingrolls for supporting the spiralled strip only on one part, is thattrouble takes place at the start of welding operation.

In the normal type of welding of plate, it is the practice at therestart of welding after an interruption for preventing possibleinefficient penetration that the tobe-welded part of the piece of platefor the next welding is laid on the welded part of the preceding piece.This practice should apply to welding for forming helical pipe. However,the normal type of the apparatus for forming helical pipe has no drivingsource for interior and exterior forming rolls (3) and (5); strip (1) isfed by means of a pinch roll (8); therefore, at the reopening ofwelding, the pinch roll (8) is rotated reversely so that the strip (8)is drawn back somewhat in the direction of arrow, to cause theto-be-welded following piece of strip laid over existing pipe thereon.As a result, the formed pipe (2) is squeezed only on the right side inFIG. 4, therefore, welding restarts with abnormal forming conditions. Assuch welding proceeds, the

formed pipe takes on a deformation, making it impossible to even resumenormal forming conditions.

SUMMARY OF THE INVENTION The present invention seeks to solve theseproblems, including the abovementioned, inherent in the conventionaltype of the apparatus for forming spiral steel pipe; and its specialcharacteristic lies in that as an improvement of the apparatus forforming pipe by spirally curling a strip of steel with interior formingrolls and exterior forming rolls, the three rows of which form atriangle when viewed in section, a mount is provided which extends inthe direction of the axis of the interior forming stand in such a manneras to cover the interior forming stand completely except the partthereof equipped with interior forming rolls; and a plurality of rows ofinterior supporting rolls are disposed on the outer surface of the mountnearly in parallel with the edges of the spiralled strip.

An object of the present invention is to provide an apparatus forforming spiral steel pipe having a good quality of the spiral seambetween the edges of the spiralled strip, as a result of infalliblyaccurate covergence edges of the spiralled strip.

Another object of the present invention is to provide an apparatus forforming spiral steel pipe with the ability to restart the weldingoperation after an interruption, while maintaining the constancy offorming conditions.

A further object of the present invention is to provide an apparatus forforming spiral steel pipe with the ability to produce steel pipe of goodquality.

These and other objects of the present invention will be made clearer bythe following description of the present invention in the light ofattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1a and lb are front and sideexplanatory views showing the principle of a prior art apparatus forforming spiral steel pipe;

H FIGS. 2a and 2b are front and side explanatory views of anotherconventional type of apparatus for forming spiral steel pipe;

FIG. 3 is a side view of the forming apparatus of FIGS. 2a and 2bshowing a problem which occurs therewith;

FIG. 4 is an explanatory plan view of the forming apparatus of FIGS. 2aand 2b, showing forming conditions at the restart of welding after aninterruption;

FIGS. 5a and 5b are front and side explanatory views of an embodiment ofthe apparatus of the present invention for forming spiral steel pipe;

FIG. 6 is a longitudinal sectional view of an embodiment of a mechanismfor controlling the positions of interior supporting rolls for use inthe forming apparatus of the present invention; and

FIG. 7 is a longitudinal sectional view of another embodiment of themechanism as shown in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIGS. 5a and 5b, a long metalstrip 11 is fed continuously into the forming apparatus by means of apinch roll (not shown) to form a; (12) indicates cylindrical pipe 12having a welded seam (s) between the edge portions of the spirallycurled strip. A plurality of interior forming rolls (13) is disposed ina row on an interior forming stand (14). Two rows of exterior formingrolls (15) are provided, one on each of two exterior forming stands 16.Each set of an interior forming roll (13) and two adjacent exteriorforming rolls (15) on the respective stands (16) are at the corners ofsaid interior forming roll (13) being at the apex thereof. These rollsare used to curl strip 11 which is supplied at a prescribed obliqueangle, into a spirally formed pipe.

According to the present invention, there is provided mount (17) whichcovers the interior forming stand (14) wholly except for the partequipped with the row ofinterior forming rolls (13). The mount (17) hasa polygonal cross-section, and extends along the long axis of theinterior forming stand (14) for a part of the length thereof. On themount (17) there are provided a great number of interior supportingrolls (18) in a plurality of plural rows (P P P each running nearlyparallel with the seam(s) between the edge portions of the spiralledstrip (12). Therefore, the disposition of interior supporting rolls (18)is also spiral, and each roll has a shaft extending nearly perpendicularto the seam(s) between the edge portions of the spiralled strip.

There is no particular distance (h) between adjacent rows of saidinterior supporting rolls (18), but it is desirable that such rollsshould be so arranged as to support the strip 11 at more than twopositions within the width (H) of the spiralled strip along the axis ofthe formed pipe and also as near as possible to both edge portions ofthe spiralled strip. As for the number (Pn) of rows of said interiorsupporting rolls, it is preferred that there be three to five rowsinordinary cases, but the invention is not limited thereto.

According to the present invention, the radial position of said interiorsupporting rolls (18) is made adjustable by providing adjusting units(19) between said interior supporting rolls (18) and the mount (17), soas to adjust the diameter of the spirally formed pipe (12). As shown inFIG. 5, a plurality of said adjusting units (19) are provided on thepolygonal mount (17), one on each face of said mount, parallel to theaxis of the formed pipe (12); and on each adjusting unit there areprovided for free rotation interior supporting rolls (18) in a numbercorresponding to the plurality of rows of such rolls. As shown, a numberof interior supporting rolls (18) are mounted on each adjusting unit(19). This is only for convenience. According to the present invention,there is no limitation on the number of such rolls on one such member,so that it is possible to set one such roll on one adjusting unit,making each roll controllable independently from the others.

For details of the adjusting unit (19.), reference is made to FIGS. 6and 7, both showing embodiments of such a member according to thepresent invention.

The adjusting unit of FIG. 6 consists of a pair of blocks, that is, aradially outer block (20) and a radially inner sliding block (21); andthe contact-sliding surface (22) of the respective blocks is in the formof wedges corresponding to each other. On the outer block (20) aremounted inner supporting rolls (18), each being on a mounting block(23). At one end of the inner sliding block (21) is a freely rotatablethreaded rod (24) connected to block (21) by an appropriate type ofjoint, and threadedly engaged with nut (25) fixed on the mount (17), sothat the turning of the threaded rod 24 causes the rod to movehorizontally through the nut (25), thereby pushing forward or drawingback the inner block (21).

As the inner block (21) moves forward or backward, the outer block movesradially outwardly or inwardly, thereby changing the radial position ofthe interior supporting roll (18). The outer block (21) is mounted onthe mount (17) only for radial movement.

FIG. 7 shows another embodiment of the adjusting unit according to thepresent invention.

The bottom of the mounting block (26) for each interior supporting roll(18) is in the form of a wedge, and contacts the wedge on the innerblock (27) directly. Therefore, the outer block (28) functions merely asa guide for the mounting block (26), supporting this block for radialmovement. Therefore, as in the embodiment of FIG. 6, the radialpositions of the interior supporting rolls 18) are changed by theturning of the threaded rod (24).

Needless to say, any other appropriate means than that described abovemay be used, according to the present invention, for making theabovementioned adjusting unit function and for horizontal movement ofthe lower block.

Also according to the present invention, interior supporting rolls aredisposed spirally in plural rows, thereby making the positions forsupporting the periphery of the spirally formed pipe by interiorsupporting rolls relatively constant as viewed sectionally of the pipe;also as such supporting is near the seams between the edge portions ofthe spiralled strip and at constant distances along the axis of thepipe, forming operations can be made stable and accurate, completelypreventing offset of the welded part which may occur due to imbalance ofthe supporting positions. Within a certain range, the height of theinterior supporting rolls can be changed by using the adjusting unit,making it possible to adjust the diameter of the formed pipe.

What is claimed is:

1. In an apparatus for forming spiral steel pipe by spirally curlingmetal strip, the apparatus having a row of interior forming rollsmounted on an interior forming stand and a plurality of rows of exteriorforming rolls mounted individually on two exterior forming stands, theimprovement comprising a mount extending in the direction of the axis ofthe interior forming stand and covering the peripherial parts of saidinterior forming stand other than the part directly supporting the'rowof the interior forming rolls; a plurality of interior supporting rollson said mount for contracting the inner surface of the pipe being formedwhere the edges of the strip have not been welded together, saidinterior supporting rolls being along a plurality of spiral lines in theperipheral direction of the pipe aligned nearly parallel with the stripedges to be joined for forming the pipe being formed.

2. The improvement as claimed in claim 1 in which said interiorsupporting rolls are in rows in the axial direction of the interiorforming stand with the rows spaced around the periphery of said mountand the interior supporting rolls in each row being in a spacecorresponding to the width of the metal strip.

3. The improvement as claimed in claim 2, wherein said interiorsupporting rolls in the rows are at positions as near as possible to theedges of the spiralled strip.

4. The improvement as claimed in claim 1, further comprising adjustingmeans for said interior supporting rolls mounted on said mount.

5. The improvement as claimed in claim 4, wherein each said adjustingmeans comprises a pair of blocks, one laid over the other, thecontacting surfaces of said blocks being in the form of wedgescorresponding to each other, the radially outer block having at leastone interior supporting roll mounted thereon and the radially innerblock having means thereon for moving said inner block relative to saidinterior forming stand and mount to move said outer block radially.

6. The improvement as claimed in claim 4, wherein each interiorsupporting roll has a mounting block on which it is mounted, and eachsaid adjusting means

1. In an apparatus for forming spiral steel pipe by spirally curlingmetal strip, the apparatus having a row of interior forming rollsmounted on an interior forming stand and a plurality of rows of exteriorforming rolls mounted individually on two exterior forming stands, theimprovement comprising a mount extending in the direction of the axis ofthe interior forming stand and covering the peripherial parts of saidinterior forming stand other than the part directly supporting the rowof the interior forming rolls; a plurality of interior supporting rollson said mount for contracting the inner surface of the pipe being formedwhere the edges of the strip have not been welded together, saidinterior supporting rolls being along a plurality of spiral lines in theperipheral direction of the pipe aligned nearly parallel with the stripedges to be joined for forming the pipe being formed.
 2. The improvementas claimed in claim 1 in which said interior supporting rolls are inrows in the axial direction of the interior forming stand with the rowsspaced around the periphery of said mount and the interior supportingrolls in each row being in a space corresponding to the width of themetal strip.
 3. The improvement as claimed in claim 2, wherein saidinterior supporting rolls in the rows are at positions as near aspossible to the edges of the spiralled strip.
 4. The improvement asclaimed in claim 1, further comprising adjusting means for said interiorsupporting rolls mounted on said mount.
 5. The improvement as claimed inclaim 4, wherein each said adjusting means comprises a pair of blocks,one laid over the other, the contacting surfaces of said blocks being inthe form of wedges corresponding to each other, the radially outer blockhaving at least one interior supporting roll mounted thereon and theradially inner block having means thereon for moving said inner blockrelative to said interior forming stand and mount to move said outerblock radially.
 6. The improvement as claimed in claim 4, wherein eachinterior supporting roll has a mounting block on which it is mounted,and each said adjusting means composes a pair of blocks, one laid overthe other, the radially outer block having at least one aperture thereinin which the mounting block of an interior supporting roll is radiallyguided, and the radially inner block having a surface in the form of awedge contacting the inner end surface of the mounting block of theinterior supporting roll and further having means thereon for movingsaid inner block relative to said interior forming stand and said mountto move said mounting block radially.